1. Field of the Invention
This invention relates generally to hydraulic steering dampers for use on motor vehicle steering systems for reducing undesirable vibrations therein. More particularly, the present invention relates to a torsional hydraulic damper for reducing steering system vibrations.
2. Disclosure Information
Steering system vibrations have challenged vehicle designers for years. Often these vibrations are exhibited to a vehicle operator in the form of an oscillating steering wheel. Many solutions have been proposed to reduce steering system vibrations, including adding friction to the steering system. These solutions frequently have a deleterious effect on some other suspension or steering system attribute. Adding friction, for instance, degrades the steering feel the steering system presents to the operator.
Another approach to reducing steering system vibrations has been to add steering dampers, much like a vehicle shock absorber as used in a vehicle suspension. These steering dampers are attached at one end to a lateral link in the steering system, such as a drag link and to the vehicle structure, such as a cross member, at the other end. Of course, the dampers have to be large enough to accommodate the steering system travel, which can make them heavy and costly. While it has been observed that these dampers are effective for attenuating very low frequency vibrations, they are not as effective at controlling higher frequency vibrations (10-20 Hz), especially at low amplitudes. Furthermore, they tend to add considerable friction to the steering system, causing it to feel heavy and numb to operators.
It would therefore be desirable to provide a steering damper capable of dampening higher frequency vibrations while not limiting the rotational travel of the steering system and not changing the feel of the steering system when the vibration control is not required.